| Abstract: | The structure and composition of thin, conductive metallic films of chromium and iridium that are typical of the coatings used for electron microscopy is described. The purpose of this study was to determine the grain size and composition of the films deposited, with thicknesses of 1 nm, 2.5 nm, and 5 nm, onto amorphous carbon films using ion beam sputtering with argon as the sputtering gas. A comparison between chromium films deposited under conditions of liquid nitrogen (LN) trapping or of no trapping revealed slight differences in their microstructure. As expected, the grain size of the films increased with the thickness, and the average grain sizes varied between 10 and 25 nm. Grain size was also found to depend on the source of ion beam energy; the correlation between grain size and beam energy was more pronounced in the iridium films than in the chromium films. This effect was greater when the deposition chamber was not LN trapped. As the ion beam energy increased from 18 W to 24 W, there was a corresponding increase in grain size in some of the films. Although transmission electron diffraction analysis indicated the presence of about 5% chromium oxide in the chromium films, no oxide was detected in the iridium films. |
